The present invention relates to a keyboard on which a number of switches are placed side by side. An object of the invention is to provide switches which can visibly display letters or symbols, printed on cards or the like disposed below the keyboard, whereby a push-button on a desired symbol is pushed so as to feed a signal into a computer which corresponds to the desired letter or symbol.
Recently, a keyboard for a system for viewing letters or symbols so as to operate a switch corresponding thereto has appeared for use as an input device for an office computer, the computer being usable by a person who is not a professional operator. A conventional example of a keyboard for the above use is to form electrodes made from NESA film on transparent glass, the electrodes being touched directly by operator's fingers so as to feed a signal; such a keyboard is deficient with respect to control touch because the operator taps the glass surface with his or her fingers at every operation. Another method is to place a flexible sheet bearing letters or symbols on a panel on which a number of opaque switches are arranged, the switches being pushed from above the sheet. This method, which always deforms the flexible sheet, creates a problem with respect to the lifetime of the flexible sheet or the defacement of the written letters. A further method is to provide the switch itself with a transparent window molded of a transparent acrylic resin, so that an operator views a card placed underneath the switch through the window and urges the window corresponding to the letters or symbols printed on the card, thereby generating the required signal. Since windows may have their transparency deteriorate due to a "sink mark" when the acrylic resin is molded, flaws produced in the window, etc.